CC-Link is a local network system that provides high-speed process control and information data processing, providing customers with efficient, comprehensive industry and process automation. Users using CC-Link can reduce the number of control variables and the power lines required for complex production lines. Therefore, users can select the appropriate equipment from the remaining 354 areas supporting CC-LINK, so the expansion of the multi-vendor environment will become very easy.
As for high-speed communication, it enables the input of the communication sensor to meet the requirements of smart devices and high-speed response requiring a large amount of data communication. As a function of CC-link, the RAS function is: standby main function, separate slave function, these functions make it automatically recover when communication failure and system debugging. As for the test and monitoring functions, it is available to confirm the data connection status, hardware test and circuit test. The CC-Link network diagram is shown in Figure 1. The monitoring system consists of Master > Slave > PC > Inverter > Servo Motor > Remote I/O Unit.
To meet the demands of automation and flexibility, many complex manufacturing systems are controlled by programmable logic controllers (PLCs). This is because the PLC is adaptable, modular, easy to use and low in purchase cost. Vacuum wound coating is such a complex manufacturing system.
This paper introduces an intelligent monitoring system based on CC-LINK fieldbus, which includes a host PC and a programmable logic controller for control and information management. This monitoring system uses the new technology of CC-Link fieldbus.
2 Structure of the monitoring system
The fieldbus-based monitoring system has two functions, including the monitoring and information management unit of the monitoring area and the control unit in the control room. All intelligent monitoring units located near the liquidation vacuum machine have microprocessors with the following functions: signal sampling, A/D conversion, data calculation, etc. The fieldbus is the most important connection between the discrete detection unit and the primary station in the unit slave. The analog signal is replaced by a digital signal to form a two-way communication to facilitate operator control, inspection, and parameter settings in the control room. This structure, on the one hand, improves the accuracy and anti-interference ability of the monitoring system, and on the other hand, saves investment costs.
The digital intelligent monitoring unit should be based on actual needs. The system has five monitoring units: temperature, vacuum, roll diameter, film tension and transmission speed.
Whether the monitoring system works properly depends on whether the performance of the sensor is above the required level, and their accuracy and stability have a direct impact on the monitoring system. The data obtained from these sensors is processed by the PLC and displayed on the HMI human machine interface, as shown in Figure 2.
The intelligent monitoring module has two functions: on the one hand, its filter, the sensor that amplifies and adjusts the output signal can be processed by PLC (FX series) to get the appropriate value; on the other hand, it uses the programmable controller of the communication interface for data acquisition. , A / D conversion, data processing, software anti-interference, calculate parameters and use the communication interface on the PLC to transfer data to the central control unit.
The Central Control Unit (CCU) is the center of the monitoring system and includes a personal computer and RS232. It works by controlling each unit of intelligent monitoring, processing the resulting data and a piece of information, and saving them. In addition, the controller supports computer access by the upper user, and its data analysis is feasible, and the data is diagnosed using data management and fault diagnosis software.
The monitoring system uses a module composed of CC-LINK field bus and a twisted pair cable as a communication medium. Up to sixty stations can be connected to this fieldbus, and the communication module connects the monitoring unit to the substation via the CC-Link fieldbus. When the fieldbus communication rate is 156kps, the transmission distance can reach 1.2km.
3 PLC programming
In this winding system, we use the Mitsubishi A-Series PLC as the master station because of its fast response capability and powerful information processing capabilities. It is used to control the behavior of the stretch coexistence system of the total winding system and the PLC winding system of the FX series. The system's operating actions and sequence of actions have been programmed into the control program by the designer. The control program sets up a series of operational actions for the winding system to guide the PLC to control the entire system. The current state of all sensors or actuators is stored as input, output or semaphore signals in the PLC memory. Therefore, the PLC program is the basis for a PLC control manufacturing system monitoring.
The main method used in PLC programming is the ladder method, which provides a design environment in which software tools run on the host terminal to facilitate construction, verification, testing, and diagnostic ladder diagrams. First, the high-level program is written in the ladder diagram; second, the ladder diagram should be converted to binary code so that they can be stored in random access memory (RAM) or memory code erasable programmable read only memory (EPROM). Each successive instruction is decoded and executed by the CPU. The function of the CPU is to control the memory and I/O interface to process data according to the program. Each I/O node on the PLC can be used to distinguish I/O addresses. The direct representation method of data is related to input, output and memory. Based on the fact, the PLC's memory is divided into three parts: input image storage, output image storage and internal memory to directly represent the input, output and memory related data.
The PLC program uses the main program cyclic scan method, for example, the input variables are periodically checked. The loop project is started by using the scan input system and the fixed position of the memory in the memory (input image memory), the ladder program is executed after the response, the scan program is used to solve the output state determined by the logic ladder, and the updated output state is stored in the fixed state. Memory location (output image memory). At the end of the program scan, the output values ​​saved in memory are used to set and reset the physical output of the PLC.
We all know that logic control is a significant feature of PLCs that can be used to efficiently process analog data.
1) Analog data acquisition and conversion Analog input and output, such as pressure and temperature, need to be measured in real time. For example, the temperature is first obtained by platinum resistance, and then the signal conversion module converts it into a voltage signal of 1-5V. The output of this conversion module is finally It is collected and transmitted to the above PLC.
2) PLC control algorithm The analog variable can be any kind of variable, such as temperature and pressure in our winding system. In fact, there are two control modes, automatic and manual. In manual mode, the operator modifies the output value according to the desired level; in automatic mode, the output value is given according to a pre-designed control algorithm. It is worth mentioning that the output of the PLC is always incremental. Although the self-tuning PID controller can meet the requirements, manual tuning is always used to initialize the regular production, and the system switches to the automatic mode; we emphasize that the user's Empirical fuzzy logic control is also used to improve production conditions. The film tension control system uses PLC's fuzzy logic controller (PLC) to overcome the uncertainty of the winding system. The fuzzy logic algorithm has been implemented by a basic PLC controller.
The parameter processing for fixed mode and conventional PID has reached a very good stage, but the stability is relative, the parameters of the winding system fluctuate within a certain range, so the controller must be robust to obtain higher performance. . For this purpose, fuzzy reasoning is used to adapt to PID control. In this way, the PID factor can be adjusted based on system status and plant parameters.
3) At the beginning of the servo motor control, the film is transported at a low speed, and then the servo motor is accelerated to a set high speed of about 8 meters per second. The sensor detects the film tension and controls the servo motor speed to maintain a constant tension. The control target must not only keep the film tension constant, but also achieve the set speed in the shortest time. Therefore, the main problem is how to control the accuracy of the servo motor.
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